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10. Pathology and Oncology MCQs

Practice Set 259 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 5161

Topic: Bone Tumors

Which of the following is an expected radiographic finding for a low-grade conventional chondrosarcoma?

. Extensive Codman's triangle.
. Hair-on-end periosteal reaction.
. Well-circumscribed lytic lesion with punctate/ring-and-arc calcifications and endosteal scalloping.
. Sunburst periosteal reaction.
. Sclerotic lesion with a thick, benign-appearing periosteal reaction.

Correct Answer & Explanation

. Well-circumscribed lytic lesion with punctate/ring-and-arc calcifications and endosteal scalloping.

Explanation

Low-grade conventional chondrosarcomas commonly present radiographically as well-circumscribed lytic lesions with characteristic punctate or ring-and-arc calcifications (representing mineralized cartilaginous matrix) and varying degrees of endosteal scalloping, indicating internal bone erosion. Codman's triangle, hair-on-end, and sunburst periosteal reactions are typical of more aggressive lesions like osteosarcoma or Ewing sarcoma. A thick, benign-appearing periosteal reaction might suggest chronic osteomyelitis or a healing fracture, not a chondrosarcoma.

Question 5162

Topic: 10. Pathology and Oncology

A patient with a presumed enchondroma in a long bone develops symptoms consistent with malignant transformation. What is the most appropriate next diagnostic step after initial radiographs?

. Immediate surgical curettage.
. Observation with serial radiographs every 6 months.
. MRI of the affected bone with contrast.
. Bone scan to rule out metastases.
. CT angiogram to assess vascularity.

Correct Answer & Explanation

. MRI of the affected bone with contrast.

Explanation

If clinical symptoms (pain) or initial radiographs suggest malignant transformation of an enchondroma, an MRI with contrast is the most appropriate next step. MRI provides superior soft tissue resolution, can assess the extent of intramedullary involvement, detect cortical breach, evaluate soft tissue extension, and often helps differentiate between benign and malignant cartilaginous lesions based on enhancement patterns and presence of soft tissue mass. Immediate surgical curettage without full workup risks inadequate treatment. Observation is inappropriate with suspicious symptoms. A bone scan might be part of staging but MRI is better for local assessment. CT angiogram is not routinely indicated for diagnosis.

Question 5163

Topic: Bone Tumors

What is the most common histological variant of chondrosarcoma?

. Clear cell chondrosarcoma.
. Mesenchymal chondrosarcoma.
. Dedifferentiated chondrosarcoma.
. Conventional chondrosarcoma.
. Juxtacortical chondrosarcoma.

Correct Answer & Explanation

. Conventional chondrosarcoma.

Explanation

Conventional chondrosarcoma is by far the most common histological variant, accounting for approximately 85-90% of all chondrosarcomas. The other variants (clear cell, mesenchymal, dedifferentiated, juxtacortical/periosteal) are relatively rare.

Question 5164

Topic: Bone Tumors

Which of the following statements about radiation therapy for chondrosarcoma is true?

. Conventional chondrosarcoma is highly radiosensitive and radiation is the primary treatment.
. Radiation therapy is contraindicated in all forms of chondrosarcoma.
. Mesenchymal chondrosarcoma and dedifferentiated chondrosarcoma may show some response to radiation due to their more aggressive, less differentiated components.
. Radiation therapy is effective for local control of Grade I lesions but not higher grades.
. Radiation therapy is used exclusively for palliation of pain in metastatic disease.

Correct Answer & Explanation

. Mesenchymal chondrosarcoma and dedifferentiated chondrosarcoma may show some response to radiation due to their more aggressive, less differentiated components.

Explanation

While conventional chondrosarcoma is generally considered radioresistant, mesenchymal chondrosarcoma and the high-grade components of dedifferentiated chondrosarcoma can show some responsiveness to radiation therapy due to their more undifferentiated nature and higher cellularity. Therefore, radiation may be considered as an adjuvant or for unresectable disease in these specific variants. Radiation is not the primary treatment for conventional chondrosarcoma and is not contraindicated in all forms. It can be used for local control in some unresectable cases, not just for Grade I, and its role is not limited to palliation in metastatic disease, although that is one application.

Question 5165

Topic: 10. Pathology and Oncology

A 60-year-old male with a history of radiation exposure for a prior malignancy develops a new, rapidly enlarging, painful mass in his ilium. Biopsy reveals a chondrosarcoma. What is the most likely etiology of this chondrosarcoma?

. Spontaneous primary chondrosarcoma.
. Malignant transformation of a pre-existing enchondroma.
. Radiation-induced chondrosarcoma.
. Malignant transformation of an osteochondroma.
. Mesenchymal chondrosarcoma.

Correct Answer & Explanation

. Radiation-induced chondrosarcoma.

Explanation

Radiation exposure is a known risk factor for the development of secondary sarcomas, including chondrosarcoma. These radiation-induced sarcomas often present with a rapidly growing, painful mass within or near the previously irradiated field, typically many years after the initial radiation treatment. Given the patient's history, radiation-induced chondrosarcoma is the most likely etiology. While spontaneous primary chondrosarcoma is the most common type overall, the history of radiation is a strong indicator for this specific etiology. The other options are less likely given the specific history.

Question 5166

Topic: 10. Pathology and Oncology

Which of the following is the most accurate statement regarding the role of positron emission tomography (PET) scans in chondrosarcoma?

. PET is the primary imaging modality for diagnosing chondrosarcoma.
. PET is highly sensitive for distinguishing between benign enchondroma and low-grade chondrosarcoma.
. PET is useful for assessing tumor metabolic activity, detecting distant metastases, and monitoring response to therapy in higher-grade lesions.
. PET is primarily used to assess bone marrow involvement.
. PET is superior to MRI for local staging of chondrosarcoma.

Correct Answer & Explanation

. PET is useful for assessing tumor metabolic activity, detecting distant metastases, and monitoring response to therapy in higher-grade lesions.

Explanation

PET scans, particularly FDG-PET, are useful for assessing the metabolic activity of chondrosarcomas, which generally correlates with tumor grade (higher grade = higher uptake). It is valuable for detecting distant metastases (staging) and monitoring response to therapy, especially in higher-grade or dedifferentiated lesions. PET is not the primary diagnostic tool nor is it highly reliable for distinguishing low-grade chondrosarcoma from enchondroma due to overlapping SUV values. It is not superior to MRI for local staging.

Question 5167

Topic: 10. Pathology and Oncology

What is the primary challenge in the pathological diagnosis of low-grade chondrosarcoma versus enchondroma?

. Distinguishing cartilaginous matrix from osteoid.
. Identifying mitotic figures, which are abundant in both.
. Assessing cellularity, nuclear atypia, and invasion of marrow spaces, which can be subtle.
. Identifying the presence of multinucleated giant cells.
. Differentiating it from fibrous tissue.

Correct Answer & Explanation

. Assessing cellularity, nuclear atypia, and invasion of marrow spaces, which can be subtle.

Explanation

The distinction between low-grade chondrosarcoma and enchondroma is notoriously challenging for pathologists. It primarily relies on subtle features such as increased cellularity, nuclear plumpness and atypia, occasional binucleation, and crucially, the permeation of marrow fat spaces by malignant cells. Mitotic figures are typically sparse or absent even in low-grade chondrosarcoma. Giant cells are not characteristic of either. Distinguishing cartilaginous matrix from osteoid is for osteosarcoma, and from fibrous tissue for fibrous tumors.

Question 5168

Topic: 10. Pathology and Oncology

A 55-year-old patient undergoes an intralesional curettage with adjuvant argon beam coagulation for a low-grade central chondrosarcoma of the proximal tibia. What is the most significant concern with this approach?

. Increased risk of pathological fracture.
. High rate of systemic metastasis.
. Difficulty with bone grafting.
. Increased risk of local recurrence due to incomplete tumor removal.
. Adverse reaction to argon gas.

Correct Answer & Explanation

. Increased risk of local recurrence due to incomplete tumor removal.

Explanation

Intralesional curettage, even with adjuvant therapy like argon beam coagulation, carries a higher risk of local recurrence compared to wide en bloc resection for chondrosarcoma. Chondrosarcomas, even low-grade, can be infiltrative, and achieving truly negative margins intralesionally can be difficult. While not universally contraindicated in all low-grade central chondrosarcomas (especially in non-weight-bearing bones or expendable bones where wide resection is morbid), local recurrence is the primary concern. Systemic metastasis is rare for low-grade tumors. Pathological fracture or bone grafting issues are secondary concerns. Adverse reaction to argon gas is not a primary concern.

Question 5169

Topic: Bone Tumors

What is the characteristic appearance of a dedifferentiated chondrosarcoma on imaging?

. A uniformly well-circumscribed lesion with punctate calcifications.
. A purely sclerotic lesion with benign periosteal reaction.
. A biphasic appearance with a chondroid component juxtaposed with a destructive, aggressive lytic soft tissue mass.
. A lesion primarily affecting the epiphysis with clear cell morphology.
. A broad-based sessile lesion arising from the cortical surface.

Correct Answer & Explanation

. A biphasic appearance with a chondroid component juxtaposed with a destructive, aggressive lytic soft tissue mass.

Explanation

Dedifferentiated chondrosarcoma typically presents with a biphasic imaging appearance, reflecting its histology. It shows features of a conventional chondrosarcoma (chondroid matrix, calcifications) adjacent to or within a more aggressive, destructive lytic lesion with cortical destruction and a significant soft tissue mass, representing the high-grade non-cartilaginous component. A uniformly well-circumscribed lesion or sclerotic lesion would suggest a low-grade or benign lesion. Epiphyseal clear cell morphology is for clear cell chondrosarcoma. A broad-based sessile lesion is characteristic of juxtacortical chondrosarcoma or osteochondroma.

Question 5170

Topic: Bone Tumors

Which molecular alteration is commonly associated with peripheral chondrosarcomas arising from osteochondromas?

. IDH1/IDH2 mutations.
. TP53 mutations.
. EXT1/EXT2 mutations.
. H3F3A mutations.
. COL2A1 mutations.

Correct Answer & Explanation

. EXT1/EXT2 mutations.

Explanation

Peripheral chondrosarcomas, which arise from pre-existing osteochondromas (especially in Multiple Hereditary Exostoses), are strongly associated with inactivating mutations in the EXT1 and EXT2 genes. These genes are involved in heparan sulfate biosynthesis and are linked to the development of osteochondromas. While IDH1/IDH2 mutations are common in central chondrosarcomas and enchondromas, EXT1/EXT2 are specific to the osteochondroma pathway of malignant transformation.

Question 5171

Topic: 10. Pathology and Oncology

A patient undergoing surveillance for Multiple Hereditary Exostoses (MHE) develops increasing pain in an osteochondroma of the pelvis. Which finding, if present, would prompt the most urgent concern for malignant transformation?

. A cartilaginous cap measuring 1.5 cm on MRI.
. Presence of a new bursal sac over the osteochondroma.
. Increased T2 signal within the cartilaginous cap without other aggressive features.
. New, irregular areas of calcification within the cartilaginous cap.
. Loss of continuity between the medulla of the osteochondroma and the parent bone.

Correct Answer & Explanation

. New, irregular areas of calcification within the cartilaginous cap.

Explanation

While an adult cartilaginous cap >2-3 cm is concerning, new, irregular areas of calcification within the cartilaginous cap, especially when associated with pain and growth, are highly suspicious for malignant transformation and represent changes within the developing chondrosarcoma matrix. A 1.5 cm cap is generally within the benign range for MHE. A new bursa is a mechanical irritation, not malignancy. Increased T2 signal can be due to fluid or benign cartilage. Loss of medullary continuity is not typical for malignant transformation, which usually involves thickening of the cap or bony erosion.

Question 5172

Topic: 10. Pathology and Oncology
What is the typical histological appearance of a Grade III conventional chondrosarcoma?
. Uniform cells with abundant intercellular matrix.
. Mildly increased cellularity with occasional binucleated cells.
. Marked cellular pleomorphism, high cellularity, obvious mitotic figures, and often necrosis.
. Small round cells with scant cytoplasm.
. Clear cells arranged in lobules with prominent reactive bone.

Correct Answer & Explanation

. Marked cellular pleomorphism, high cellularity, obvious mitotic figures, and often necrosis.

Explanation

Grade III conventional chondrosarcoma is characterized by high cellularity, significant nuclear pleomorphism, obvious mitotic figures (which are rare in lower grades), and often areas of necrosis. This reflects its aggressive malignant nature. Uniform cells or mildly increased cellularity characterize lower grades. Small round cells are seen in mesenchymal chondrosarcoma. Clear cells are seen in clear cell chondrosarcoma.

Question 5173

Topic: 10. Pathology and Oncology

What is the most common presenting symptom of an axial skeleton (e.g., pelvis, sacrum, spine) chondrosarcoma?

. Pathological fracture.
. Rapidly progressing neurological deficit.
. Deep, dull, persistent pain, often worse at night.
. Palpable mass that is mobile and non-tender.
. Acute onset severe pain with swelling.

Correct Answer & Explanation

. Deep, dull, persistent pain, often worse at night.

Explanation

Axial skeleton chondrosarcomas often grow silently for a long time before symptoms appear. The most common presenting symptom is deep, dull, persistent pain, which may be worse at night and progressive. Pathological fractures can occur, but are less common than pain. Neurological deficits occur if the tumor compresses neural structures. A palpable mass might be present but often deep and fixed. Acute severe pain is less common unless there's a pathological fracture or rapid dedifferentiation.

Question 5174

Topic: 10. Pathology and Oncology

In the surgical management of a low-grade chondrosarcoma, which approach, if feasible, is associated with the best long-term local control rates?

. Intralesional curettage.
. Marginal excision.
. Wide en bloc resection.
. Amputation.
. Radiation therapy alone.

Correct Answer & Explanation

. Wide en bloc resection.

Explanation

Wide en bloc resection, achieving a clear margin of healthy tissue around the tumor, is associated with the best long-term local control rates for chondrosarcoma of all grades, including low-grade. While marginal excision can be considered for very select low-grade tumors and intralesional for specific situations, wide resection remains the gold standard for oncological safety. Amputation is a last resort. Radiation therapy alone is generally ineffective for conventional chondrosarcoma.

Question 5175

Topic: 10. Pathology and Oncology

A 50-year-old male has an incidental finding of a lesion in his proximal humerus. Radiographs show punctate calcifications within a lobulated intramedullary lesion with mild endosteal scalloping. There is no pain. Biopsy confirms Grade I chondrosarcoma. What is the most appropriate management?

. Intralesional curettage.
. Wide en bloc resection of the proximal humerus.
. Observation with serial MRI scans.
. Radiation therapy.
. Systemic chemotherapy.

Correct Answer & Explanation

. Wide en bloc resection of the proximal humerus.

Explanation

For a low-grade (Grade I) chondrosarcoma, particularly in the proximal humerus where limb salvage and functional preservation are paramount, wide en bloc resection is the most appropriate management to achieve local control. While observation might be considered for extremely indolent, asymptomatic enchondromas, a confirmed Grade I chondrosarcoma, even if asymptomatic, warrants definitive surgical treatment due to its malignant potential and risk of progression. Intralesional curettage may be considered in very selected, small, non-aggressive lesions where risks of wide resection are high, but wide resection offers the best local control. Radiation and chemotherapy are ineffective as primary treatments for conventional chondrosarcoma.

Question 5176

Topic: 10. Pathology and Oncology

Which of the following is considered the gold standard for definitive staging of chondrosarcoma to identify distant metastases?

. Bone scan.
. CT scan of the chest, abdomen, and pelvis.
. MRI of the primary lesion.
. PET-CT.
. Plain radiographs of the entire skeleton.

Correct Answer & Explanation

. CT scan of the chest, abdomen, and pelvis.

Explanation

For definitive staging of chondrosarcoma to identify distant metastases, a CT scan of the chest, abdomen, and pelvis is the gold standard. The lungs are the most common site of metastasis, making chest CT crucial. Abdomen/pelvis CT is important for other potential sites, especially for primary pelvic tumors. While PET-CT can be very useful for assessing metabolic activity and detecting metastases, CT of the chest is still generally considered the primary standard for lung metastasis detection. Bone scans are sensitive but non-specific and may not pick up all metastases. MRI is for local staging.

Question 5177

Topic: 10. Pathology and Oncology

What is a potential complication of intralesional curettage for chondrosarcoma, even with adjuvant therapy?

. Increased systemic toxicity.
. Reduced joint function due to excessive bone removal.
. Persistent pain requiring long-term opioid use.
. Local recurrence at the surgical site.
. Accelerated malignant transformation.

Correct Answer & Explanation

. Local recurrence at the surgical site.

Explanation

The most significant and well-documented complication of intralesional curettage for chondrosarcoma is local recurrence at the surgical site. This is due to the infiltrative nature of the tumor cells and the difficulty of achieving truly clear margins with this technique. While intralesional curettage aims to preserve joint function, incomplete tumor removal increases recurrence risk, which can be more challenging to manage. The other options are less direct or less common complications of this specific surgical approach.

Question 5178

Topic: 10. Pathology and Oncology

A patient is diagnosed with a Grade II chondrosarcoma of the proximal femur. Considering its location and grade, what factor will most significantly influence the decision between limb salvage and amputation?

. Patient's age and comorbidities.
. Size of the tumor and its extent of extraosseous involvement.
. Presence of a pathological fracture.
. Patient's preference for a specific type of reconstruction.
. Availability of adjuvant chemotherapy.

Correct Answer & Explanation

. Size of the tumor and its extent of extraosseous involvement.

Explanation

The size of the tumor and its extent of extraosseous involvement, particularly compromise of the neurovascular bundle or significant muscle groups, are the most critical factors determining the feasibility of limb salvage versus amputation for a proximal femur chondrosarcoma. If wide surgical margins cannot be achieved without sacrificing essential neurovascular structures or if the tumor is too extensive to reconstruct functionally, amputation becomes necessary. While patient's age and preferences are important, they are secondary to oncological principles and surgical feasibility.

Question 5179

Topic: Bone Tumors

Which of the following describes the most common type of chondrosarcoma to affect the small bones of the hands and feet?

. Dedifferentiated chondrosarcoma.
. Mesenchymal chondrosarcoma.
. Periosteal chondrosarcoma.
. Secondary chondrosarcoma arising from a solitary osteochondroma.
. Secondary chondrosarcoma arising from enchondromatosis (e.g., Ollier's disease).

Correct Answer & Explanation

. Secondary chondrosarcoma arising from enchondromatosis (e.g., Ollier's disease).

Explanation

While conventional chondrosarcoma can occur in the small bones, malignant transformation of enchondromas, particularly in the context of enchondromatosis (Ollier's disease or Maffucci's syndrome), is the most common cause of chondrosarcoma in the small bones of the hands and feet. These typically present as low-grade chondrosarcomas. Other variants are less common in these locations.

Question 5180

Topic: 10. Pathology and Oncology

A 45-year-old female presents with a lesion in the vertebral body. Biopsy indicates a chondrosarcoma. Which of the following features would histologically favor a low-grade conventional chondrosarcoma over a chordoma, which can also occur in this location?

. Presence of physaliferous cells.
. Immunoreactivity for S-100 protein.
. Absence of extracellular myxoid matrix.
. Presence of cytokeratin positivity.
. Location in the clivus.

Correct Answer & Explanation

. Presence of physaliferous cells.

Explanation

Both chondrosarcoma and chordoma can occur in the vertebral body and both can show S-100 positivity, but chondrosarcoma typically shows stronger and more widespread S-100 immunoreactivity. However, the presence of physaliferous cells (vacuolated cells with bubbly cytoplasm) and cytokeratin positivity are classic immunohistochemical and histological hallmarks of chordoma. Chondrosarcomas have a chondroid (cartilaginous) matrix, which is different from the abundant myxoid matrix of chordoma. Clivus location is more classic for chordoma. Therefore, the presence of physaliferous cells or strong cytokeratin positivity would lean towards chordoma.

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